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8/20/2019 Wireless Debug Techniques
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Prior to class:
ı
Verify each scope has the latest firmware (and the same firmware) and K0ı Verify each scope has at least 2 passive probes (Active probes will not be used
for this particular class)
ı Verify each scope has a demo board, USB cable for power to demo board,
SMA-BNC connector doe demo board, Demo Board Case
ı Verify each scope has at least one MSO cable set (should have two, only one
will be used for this class). Connect MSO cable set 0-7. Ensure all of the flying
leads are connected properly and numbered.
ı Connect each demo board to the USB connector on the scope. Connect
RFOUT to channel 4 of the scope.
ı Load “FAST_Wireless_Debug_fhop.dlf ” into the \Documents and Settings\All
Users\Documents\Rohde-Schwarz\RTO\SaveSets\ directory (This is the default
folder when the RTO opens a file) This file is out on the RSA Cloud
ı Lay out 2 passive probes.
9/9/2013 FAST: Advanced Triggering 1
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Instructor:
Hands-on Class: Embedded
Wireless Debug Techniques
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating : The key to unraveling the mysterious correlation between time
and frequency.
ı
Triggering considerations and Triggering on Serial Busesı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 3
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating : The key to unraveling the mysterious correlation between time
and frequency.
ı
Triggering considerations and Triggering on Serial Busesı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 4
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Complex Embedded Systems
D/A
D/A
DSP
Micro controller
IQ modulator
Digital signals
Analog signals
RF signals
Oscillator
Flash
I/O
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The Challenge of Debugging Embedded Systems
ı
Baseband digital, RF and analog signals are interdependent Feedback control of RF by microcontroller
Low speed serial busses
Critical timing relationships
Interference between RF and digital signals
EMI related issues and interference problems
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating: The key to unraveling the mysterious correlation between time and
frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 7
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Using an FFT for Spectrum Analysis
Different techniques exist for viewing multiple domains on a single
instrument
Performing an FFT (Fast Fourier Transform) on a captured analog
waveform enjoys the following benefits:
ı Every analog channel is also an RF channel
ı Inherent synchronization between time and frequencyı Wide frequency band capture
ı Time gating can be used to locate causal effects
The quality and speed of measurement relies on
ı
A good input system Dynamic Range with clean ADC and low noiseı HW based processing for fast FFT updates even with deep memory
ı “Spectrum Analyzer Like” setup hiding complexity of acquisition setup
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Fourier Transform Concept
Any real waveform can be producedby adding sine waves
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Spectrum Analyzer
ı Spectrum is measured by sweeping the local oscillator across the band of
interest
Very low noise due to IF gain and filtering
Sweep can be fast over narrow span Real time operation possible using FFT after IF filter
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Spectrum Measurement is a Function of TimeGlitches
time
f 1 f 2 f 3 f 4 f 5 f 6 f 7
Measurement frequency
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FFT: Instantaneous Spectrum
f 1 f 2 f 3 f 4 f 5 f 6 f 7
f 1 f 2 f 3 f 4 f 5 f 6 f 7
f 1 f 2 f 3 f 4 f 5 f 6 f 7
t i m e
f 2 f 3 f 4 f 5 f 6 f 7f 1
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Frequency Domain Analysis
FFT Basics
ı NFFT Number of consecutive samples (acquired in
time domain), power of 2 (e.g. 1024)
ı ∆ f FFT Frequency resolution (RBW)
ı tint integration time
ı f s sample rate FFT
s FFT N
f t
f int
1
Integration time tint
NFFT samples input for FFT
FFT
Total bandwidth f s
NFFT filter output of FFT
FFT f ts
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FFT Implementation
Digital Down Conversionı
Conventional oscilloscopes Calculate FFT over entire acquisition
ı Improved method:
Calculate only FFT over span
of interest
f C = center frequency of FFT
=> FFT much faster & more flexible
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating: The key to unraveling the mysterious correlation between time and
frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 15
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Time Gating
•Signal characteristics change over the acquisition interval
•Gating allows selection of specific time intervals for analysis
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Time GatingTg
g T f
1
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Time Gating – A key to debug
ı
Frequency spectrum isoften a function of time
Locking of a PLL
EMI caused by time
domain switching
ı Time gating allows the
user to select a specificportion of the waveform
for frequency domain
analysis
Window limits frequency
resolution
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating: The key to unraveling the mysterious correlation between time and
frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 19
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20
Triggering
l Events of interest for debug can occur in any domainl Time Domain Analog (edge, runt, width, etc.)
l Time Domain Digital (pattern, serial bus)
l Frequency Domain (amplitude/frequency mask)
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21
Typical Analog Triggers
Glitchl typically narrow pulse, e.g. caused by cross-talk
Transition timel slow / fast edges, e.g. circuit instability / radiation of troublesome energy
Statel logical combination of various channels, e.g. troubleshooting parallel busses
Widthl defined pulse width, e.g. observing Inter-Symbol-Interference (ISI)
Runtl limited amplitude, e.g. meta-stable conditions in digital systems
Setup & Holdl timing relation between 2 channels, e.g. synchronous data interface
Windowl event that enters / exits a window , e.g. capture bus contentions
Time outl dead time, e.g. system errors by wrong dead time relations to other signals
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22
Time Domain Mask
l Draw a violation zone or zones
l Set for “stop on failure”
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NW4C Oscilloscope Training | Serial bus | 23
l Most Serial Bus Architectures rely on the concept of Abstraction Layers or
a Protocol Stack to transmit information fewer physical lines.
l Since an Oscilloscope captures the analog information (Physical Layer) itoften contains the root information for viewing protocol as well.
Protocol or Packet Triggering
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Application Layer
Physical Layer
Data Link Layer
Network Layer
Transport Layer
Application Layer
Bit Stream
T
r a n s m i t D a t a
R
e c e i v e D a t a
Physical Link
Framing/Packets
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NW4C Oscilloscope Training | Serial bus | 24
Example: RS232/UART
Trigger Types:
• Start bit
• Frame start
• Packet start
• A specified symbol
• Parity errors, and breaks• Frame errors
• Stop errors
• A serial pattern at any or a specified position
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25
Frequency Domain Mask
l
Mask test on spectruml Set for “stop on failure”
Frequencymask
Gated FFT
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating: The key to unraveling the mysterious correlation between time and
frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 26
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Oscilloscope Familiarization
ı Focused on operation of the RTO, assumes
basic knowledge of Oscilloscopes.
Ensure this is the latest version, as this is a
standard section of all Hands on FAST
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Interface Overview
09.09.2013 28
Signal Bar(Location to where
active waveforms and
results reside in icon
form. Can contain
both Signal icons and
result icon.)
Tool Bar(Quick access to commonly used functions)
Smart Grid(Flexible drag and drop
diagram / measurement
display)
Menu Bar( Complete Access to all
functionality)
Quick Start Guide
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Tool Bar
09.09.2013 29
Helpful Things to
know:Tool bar operates on a
“touch” basis (not drag and
drop). Simply touch the tool
you want to use and then thewaveform, result window, etc
Select can also act as
“unselect” for instance when
you are done drawing a
mask window
The toolbar can be
customized in the
DisplayToolbar menu
Everything in the tool bar is
available elsewhere in the
interface.
To configure a measurement
or select a differentmeasurement type, tap the
tool icon in the results
window that appears on
screen.
UNDO (see manual for things that cannot be revoked)
REDO
Tool Tip (Enables the tooltip display)
Show / Hide signal bar
Select / Unselect
Hardware zoom (Changes the Horiz & Vert) instrument settings
Zoom (Display with zoom diagram)
Coupled zoom (Creates a coupled zoom area and its related zoom diagram.)
Cursor (Displays vertical and horizontal cursors & performs a cursor measurement.)
Masks (Tap the icon and then tap the points that build the mask. Double-tap the last point to finish)
Vertical histogram
Horizontal histogram
Measurement
FFT
Search (Performs a search according to the settings in the "Search Setup" dialog box. )
Delete ( Removes zoom and histogram areas and their associated diagrams; measurement areas
and their associated results; and mask segments. The icon also switches off a waveform.)
Find level (Sets the trigger level to 50%.)
Quick Start Guide
A ti i l ill h
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Signal BarHelpful Things to
know:
If you need the complete
screen to see the diagrams,
you can alter the behavior of
the signalbar in the toolbar or
the DisplaySignal Bar
menu.
If more than 5 items are on
the signal bar . Clicking and
vertically dragging between
one of the signal icons willscroll through the signals.
Remember the UNDO button
if you don’t like something
that happened using the
signalbar.
Waveforms,
Measurements,
decode tables, (and
nearly anything) can be
dragged onto the
signal bar
Signal bar will highlight
when something is
ready to be dropped
onto it
Active signals will show
information about the
signal and be
displayed in the
SmartGrid.
Waveforms, are in“Minimized” state when
an icon of the actual
waveform appears in
the signal bar instead
of a waveform in the
SmartGrid.
This is achieved one of
two ways
1) A single click on the
top bar
2) Dragging a
waveform from the
Smartgrid onto the
signal bar.
Minimized waveforms
can be dragged back
onto the SmartGrid fordisplay.
Clicking the “X” from
the minimized state will
turn the signal off.
(Signal then needs to
be turned on from the
front panel or in menu
system.Quick Start Guide
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SmartGridHelpful Things to
know:You can always tap the
Icon from the toolbar and
then tap a waveform to turn itoff.
Measurements need to be
dragged from the numbers
not the top of the toolbar
To change the size of the
new diagram, drag its edge
to the new position.
SmartGrid can display up to
XX different waveforms,
result windows, tables, etc
When something is tabbed
(dragged onto placement 4),
it is now hidden from view in
a different tab. Select the
tab of the window you want
displayed on top.
SmartGr id posi t ion s
1 = Placement will be in existing diagram (overlay of signals),
creates floating icon for results.
2 = New diagram (Grid) on the left or right
3 = New diagram (Grid) above or below
4 = New tab (similar to a sheet in an Excel notebook)
5 = XY-diagram 6 = YX-diagram (only available in certain configurations)
Smart Grid works through
Drag and Drop. Two things
control what happens in the
Smart Grid
1, What you drag onto the
SmartGrid. Waveforms and
Results boxes will behave
slightly different.2. Where you drag it. See the
descriptions below.
Quick Start Guide
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Setting up a multiple channel measurementı Press “PRESET:
ı Connect CH1 to RARE_SIG on the demo board,
ı Connect CH2 to 10_MHZ_CLK
ı Toggle Demo Board DOWN button until 8 is displayed.
ı Press “AUTOSET”
ı Note that this is two signals overlayed
ı Have users adjust Vertical and Horizontal position and Scale here to line up two
measurements in one window like below. (~40ns/div, 1V/Div on each channel).
ı
Note the use of the colors to indicate the different waveform in focus. Math and Ref willalso display in alternate colors.
ı Also note that vertical controls all time bases.
09.09.2013 Quick Start Guide 32
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Similar Display Using Smart Grid
ı Press Autoset Again.
ı Minimize both channels (tapping on the channel icon)
ı Move CH1 onto smart gridı Move Channel two around the screen and show the smart grid locations. Drop
it below CH1
ı Change Horizontal scaling to 20ns/div. Note the vertical scaling has not been
reduced, it is the auto set default ~500mV/div
09.09.2013 Quick Start Guide 33
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Using Toolbarı Start the same display as the smart Grid demo.
ı Discuss the Tap-Tap or Tap-Drag mentality of the tool bar.
ı
Have them execute a zoom on C21 to isolate the pulse.ı Point out the Mask Function, utilize this to draw a square mask in the zoomed window.
Note that it is a tap-tap (tap, tap tap), not a tap-drag. Also show the select tool and how
this “unselects”: the mask. They may notice an error coming across occasionally and
turning the mask red. This error is occuring 1/s and is very rare.
ı Show how to use the trash can to delete the mask, and then the zoom window. Note that
if a mistake is made you can press undo. Add back the zoom window undo. to
09.09.2013 Quick Start Guide 34
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Display Menuı Change demo board to “0.” (10, but the period indicated the 10).
ı Press Preset – note that only channel one is active now. We want this, but if they pressed
this and wanted channel 2 or any other channel to autoset, they need to turn it on first
(including MSO channels)
ı Press Autoset. Change horizontal scale to 20ns/div
ı Press the DISPLAY hard Key. Enable infinite persistence.
ı Show how to use the intensity knob. Pressing toggles different display and dialog
settings. Use the main control intensity to raise the intensity of the display to 100%
ı Shortly a runt pulse should appear.
ı Note the level of the runt pulse (good time to highlight the annotated grid).
ı They can remember or jot this down. For to set the trigger. (should be ~2.3V with clear
areas at 2.8V and 1.85V)
09.09.2013 Quick Start Guide 35
Can also highlight
dots mode and colortables the DISPLAY
menu.
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Trigger Menuı Keep the same configuration. Press PRESET and AUTOSCALE. Change horizontal scale
to 20ns/div
ı Press the TRIGGER hard key or show how to get their from the menu system.
ı Point out the source selection. If they had an MSO or other channel to trigger on, it can be
selected here.
ı Select trigger type “RUNT” from the flyout, but point out the other selections.
ı Set the upper and lower limits to the “white space” around the runt we saw in the display
exercise. (clear areas should be at ~2.8V and ~1.8V) – NOTE Scope will not appear
triggered, important lesson here!
ı Close the window, show the that the LEVELS knob when toggled can control both the top
and bottom runt levels. Still keep them at the same levels (~2.8V and ~1.8V)
ı Explain the trigger MODE and have them press the MODE button. Now the scope is
triggered.
09.09.2013 Quick Start Guide 36
Note that this error is
1/s. In Auto mode,the scope paints
screen captures in-
between trigger
events.
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Agenda
In this workshop we’ll be learning ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating : The key to unraveling the mysterious correlation between time
and frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 37
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Hands on Lab
ı Hands On Example: Debug of noise issue on
digitally-controlled attenuator chain
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What are we going to look at
ı The 5 ATTEN bits show the digital signal that sources a digitally-controlled
attenuator chain that controls the signal strength at the RFOUT port.
ı The ATTEN bits form a 5-bit word which is 3dB per LSB.
9/9/2013 FAST: Advanced Triggering 39
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Our signal in the Frequency Domainı Connect RF out of the demo board to CH1 utilizing the SMA-BNC cable.
ı Set Demo board to demo #1 (LED=1)
ı Press PRESET..
ı Note that the RTO will default to 1MΩ setting. Explain this and show how to change into
the direct 50Ω path. Also note the diagram change in the dialog box.
ı Press AUTOSCALE (note that if Autoscale was done before the input path was altered, it
would not have scaled properly. )
ı Perform FFT on this signal (settings, 825MHz CF, 50MHz Span, 100KHz RBW). Discuss
the similarities of the settings here and what you’d find on a spec an.
9/9/2013 FAST: Advanced Triggering 40
Ch h di i ll d i l
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Change to the digitally attenuated signalı Toggle Demo board to demo #3 (LED=1)
ı Immediately you should start to see the signal amplitude raise and lower on screen.
ı Users may also see a glitch that appears on screen. We will change some settings to
make this more obvious.
ı Press the DISPLAY Hard Key and select “use color table” any are OK, I’ve chosen
spectrum these screen shots.
ı Note that his visual of the broad band noise glitch is a direct function of the FFT
processing discussed earlier. This signal IS NOT visible on all instruments (even those
claiming to have a spectrum channel.
ı Also point out that the lowest setting of this attenuator block is ~75dbm, but we can still
see the smallest signal. (for those interested, it is actaully fully attenuated on demo
setting 2).
9/9/2013 FAST: Advanced Triggering 41
Th B d b d Glit h
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The Broad band Glitchı Let’s first take a look at the broadband glitch in the frequency domain.
ı Note that users have already seen the time domain mask, but that it also works
in the frequency domain.ı Have them draw a mask (tap, then tap, tap…).
ı Have them set up a “stop on violation”
ı They should catch a glitch.
9/9/2013 FAST: Advanced Triggering 42
Note: if the mask is drawn too close tothe noise floor, smaller glitches will be
caught. The material is based on the
big glitch (although you can do the
same with the small ones)
Th B d b d Glit h
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The Broad band Glitchı Have the users press the “HISTORY” button. By pressing History, we can see
the preceding acquisitions and spectrums displayed. (Although they don’t
contain the clue to this puzzle, YET). Move back to time 0ı With the time domain trace, we can see the burst of noise. Zoom in on this
noise.
ı Also have them set a marker measurement on the burst (use the cursor tool tip
and drag a window around the burst). The bursts will vary in time but might be
between 300ns and 550ns.
9/9/2013 FAST: Advanced Triggering 43
Wh t ld b i lit h?
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What could be causing our glitch?
ı An interim step to debug of this system might be to probe with a sniffer probe to
see if there is any broadband EMI that is coupling into our channel. (alsopossible with the RTO ) Let’s assume this was done, and nothing obvious
appeared.
ı In thinking about the design, we remember the digital attenuation chain is
controlled by a 5 bit signal.
ı The 5 bit value is the attenuation factor such at 00 is the least amount of
attenuation 0dbm) , and 1F is the largest amount (-93dbm, ~-75dbm realized)
ı Let’s use the logic channels to view these signals.
9/9/2013 FAST: Advanced Triggering 44
C ti d bli th l i h l
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Connecting and enabling the logic channels
9/9/2013 FAST: Advanced Triggering 45
Connect Logic ChannelsGND GND
Logic D0 ATT0
Logic D1 ATT1
Logic D2 ATT2
Logic D3 ATT3
Logic D4 ATT4
T i d i th l i h l
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Turning on and using the logic channels
ı Logic Channels are accessed from the ProtocolParallel buses
Configuration menu on the menu bar (Note that in future FW releases, theProtocol Menu will be updated to be Analysis.)
ı Turn on Channels D0-D4. Select “Show Bus. All other settings should be
default.
ı Close the window
ı The logic channels will not appear until “Run” is pushed again. Then they will
appear.
9/9/2013 FAST: Advanced Triggering 46
T i d i th l i h l
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Turning on and using the logic channelsı Press “Run” again.
ı Until the glitch is caught, you can see the digital bus appears as a counting value up
and/or down.
ı Wait until Glitch is captured.
ı Once the glitch is captured by the mask, have the users press the “HISTORY” button.
ı Go back in time using the history button and confirm the sequence leading up to the
glitch. It should be a counting pattern that is increasing or decreasing (either can be the
case) until the glitch occurs.
9/9/2013 FAST: Advanced Triggering 47
T i d i th l i h l
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Turning on and using the logic channelsı Return to the ‘0’ moment in time (when the glitch occurred).
ı Notice the ’00’ that appears on the digital bus.
ı This ’00’ is out of sequence is somewhat time aligned with the broadband glitch.
ı Use the markers to measure both the glitch duration in the analog waveform and in the
digital waveform (digital waveform should include the transition signals afterward as well).
(either move the markers that are still out there, or put a new set down with the market
toolbar icon.)
ı These two should be roughly the same duration. (Analog may be slightly longer)
9/9/2013 FAST: Advanced Triggering 48
T i d i th l i h l
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Turning on and using the logic channelsı Let’s clean up the display:
Minimize the analog waveform (tap the signal bar CH1 box) to make the digital signals
easier to see.
Turn off the cursors by tapping the green wrench and unchecking enable on both C1
(cursor1) and C2 (Cursor2). Also minimize the mask (don’t turn off).
Move the “Bus” view in the zoom window by selecting it in the display window and using
the vertical position knob to move it up.
Scale the digital signals a bit (select them on screen and use the vertical scale and
position knobs to scale and move them)
9/9/2013 FAST: Advanced Triggering 49
T rning on and sing the logic channels
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Turning on and using the logic channelsı Notice that all of the signals are transitioning at slightly different times. (Below, bit 4 is
slow to rise from 01)
ı This difference in transition time causes a temporary (but long enough) state of ‘00’ on the
bus, which sets the attenuator chain briefly to -0bdm. This is the cause of the broad
band glitch we are seeing.
ı The fix would be to work on the digital circuit to clear up the timing issues. The Logic
channels would contine to be a valuable resource due to their timing resolution.
9/9/2013 FAST: Advanced Triggering 50
Agenda
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Agenda
In this workshop we’ll be learning
ı The challenges of debugging embedded systems
ı Frequency domain analysis and FFT basics
ı Time gating : The key to unraveling the mysterious correlation between time
and frequency.
ı Triggering considerations and Triggering on Serial Buses
ı Oscilloscope Familiarization
ı Hands On Example: Debug of noise issue on digitally-controlled attenuator
chain
ı Hands On Example: Measurement and Triggering of a frequency hopping signal
and VCO settling time.
9/9/2013 FAST: Advanced Triggering 51
Hands on Lab
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Hands on Lab
ı Hands On Example: Measurement and Triggering of a frequency
hopping signal and VCO settling time.
What will we be looking at?
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What will we be looking at?
9/9/2013 FAST: Advanced Triggering 53
Microcontroller
SPI Input Control
Signal
u1
x2
x1 * / *VCO
CPV
RFOUT
Connect to the Demo Board
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Connect to the Demo Board
ı RFOUT connects using SMA to BNC into CH4 of the Oscilloscope
ı Connect CH2 to the CPV Signal on the demo board
ı Toggle Demo Board to Demo ‘4’ ı Load FAST_Wireless_Debug_fhop.dlf (FILE hardkey ‘Open…’ )
9/9/2013 FAST: Advanced Triggering 54
Since we are using a config
file, it is important these
connects are exact.
Connect Logic Channels:
GND GNDLogic D0 SPI_CLK
Logic D1 SPI_DATA
Logic D2 PSI_CSL
Logic D3 UART/LIND0
D1
D2
D3
Initial View and Explanation
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Initial View and Explanationı The Explain to the users what they are looking at in the various windows that will appear
ı All of the windows are labeled, so utilize this
ı Note the signal bar is off by default. If they want it back simply tap the signalbar icon on
toolbar:
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ı This is the “hop”
from 835MHz down
to 825MHz.
ı The two FFT’sindicate a “safe”
settle time for the
VCO. This could be
validated with the Rx
Device Spec.
ı See Speaker notes
for more info.
Changing the view
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Changing the viewı Either by selecting and dragging, or using the navigation knob after selection, move the
right gated FFT to approximately where the CPV label is located (during the overshoot of
the CPV)
ı IMPORTANT NOTE: The system is a little slower right now since there is a lot going on,
and the memory depth is set to 10Msa. This is a lot of data to process.
ı This measurement would allow us to understand more about the overshoot caused by the
CPV. We would then check with the specification for the Rx device of this signal and
understand if it can accept this much overshoot. We could filter or modify the CPV circuit
to improve if needed.
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Triggering on another part of the hop
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Triggering on another part of the hopı There are 3 different SPI commands that control this VCO.
Tune 825MHz: (835->825) = SPI MOSI pattern: 14 80 14
Tune 815MHz: (825->815) = SPI MOSI pattern: 14 40 14
Tune 835MHz: (815->835) = SPI MOSI pattern: 14 C0 14
ı Have the user enter the other two values in the protocol trigger menu. You will see that
the tune to 815MHz is also well behaved, but the hop from 815MHz835MHz is pretty
wild. The zoom can be position on top of the voltage transition to see the impact here.
ı If time permits, you can also add a cursor to this window to measure the settle time.
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Conclusion
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Conclusion
What we learned
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What we learned.
ı When digital signals are controlling analog or RF signals within a circuit, it is
important to think in both time and frequency.
ı Many triggering and mask techniques can be used.
We can start in the frequency domain with something we don’t like or didn’t
expect to see.
We can start in the time domain with something that is known like a serial
control signal.ı Using a “frequency gate” or “time gate” can allow us to “back into” the root
cause of a problem.
ı A fast updating FFT can be critical to capturing detailed and complex transitions
that occur during anomalous behavior.